I've posted this problem in Stackoverflow (https://stackoverflow.com/questions/54639778/why-am-i-getting-this-deprecated-warning-mongodb/54639983?noredirect=1#comment96081778_54639983).
I'm working with MongoDB in NodeJS,
and when the last c.getUser statement is executed (that's to say, when I make a SECOND connectio) Mongodb outputs this warning:
But I'm not using any deprecated options. Any ideas?
After a little discussion with molank in the comments, it looks like open several connections from the same server is not a good practice, so maybe that's what the warning is trying to say (badly I think). So if you have the same problem, save the connection instead of the mongo client.